The former government jet - sold off due to escalating repair costs - has been refurbished by a private firm and flown to destinations such as Paris, New York and Barbados.
The Dáil's Public Accounts Committee (PAC) quizzed Department of Defence boss Maurice Quinn about the sale of the Gulfstream IV jet for €418,000, more than €300,000 less than its estimated value.
Sinn Féin TD David Cullinane criticised the sale process and said the aircraft's new owners, US-based Journey Aviation, have insured it to the value of $5m (€4.6m).
Fine Gael TD Noel Rock said highlighting the insurance valuation was an "unfair comparison".
He insisted the Government saved money by selling the aircraft, given the repair costs that would have been incurred had it been retained and kept in service.
A Comptroller and Auditor General (C&AG) report said an informal valuation prior to the 2015 sale estimated the aircraft as below €750,000. Spare parts - later sold for €53,000 - were previously valued at more than €400,000.
Mr Quinn insisted he was "satisfied with the value achieved" in both sales due to the "exceptional circumstances involved".
He said a €2.5m engine overhaul was due by 2019. Government had only approved maintenance costs of €400,000 a year. Other repairs in 2014 would have cost €1.34m.
He said selling "was considered to be the only viable option". At the time the jet was stripped down at a Gulfstream facility in the US.
Mr Cullinane told TDs the plane was back in use and had been flown to Paris and Barbados.
"That to me is a far cry from this jet in pieces in a hanger... that's now flying around the world, making money for some company," he said.
Mr Quinn said he wouldn't comment on a service being provided by an independent party.